Human Anatomy Vol 1

(mdmrcog) #1
UPPER LIMB

Muscle
Pectoralis major
(Fis. 3.21)

Nerve supply
Medial and lateral pectoral nerves

Table 3.2: Nerve supply and actions of muscles

Pectoralis minor
(Fig. 3.25)

Subclavius
(Fig. 3.12)

Medial and lateral pectoral nerves

Nerve to subclavius from upper trunk of
brachial plexus

Actions

. Acting as a whole the muscle causes: Adduction and
medial rotation of the shoulder joint (arm)
. Clavicular part produces: Flexion of the arm
. Sternocostal part is used rn



  • Extension of flexed arm against resistance

  • Climbing
    . Draws the scapula forward (with serratus anterior)
    . Depresses the point of the shoulder
    . Helps in forced inspiration
    Steadies the clavicle during movements of the shoulder
    joint. Forms a cushion for axillary vessels and divisions
    of trunks of brachial plexus


Manubrial fibres

Sternocostal fibres

Aponeurotic fibres

(b)
Figs 3.21a and b: (a) The origin and insertion of the pectoralis major muscle, and (b) the bilaminar insertion of the pectoralis major.
The anterior lamina is formed by the clavicular and manubrial fibres; the rest of the sternocostal and abdominal fibres form the
posterior lamina. Part of the posterior lamina is twisted upside down

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muscle of the abdomen. Out of these only the fibres
from the sternum and aponeurosis are twisted around
the lower border of the rest of the muscle. The twisted
fibres form the anterior axillary fold.
These fibres pass upwards and laterally to get
inserted successively higher into the posterior lamina
of the tendon. Fibres arising lowest, find an opportunity
to get inserted the highest and form a crescentic fold
which fuses with the capsule of the shoulder joint.

ir,atTesting
i. The clavicular head of the pectoralis major can be
tested by attempting to lift a heavy tablelrod. The
sternocostal head can be tested by trying to depress
a heavy table/rod.

ii. The clavicular head is made prominent by flexing
the arm to a right angle (Fig. 3.22).The stemocostal
head can be tested by extending the flexed arm
against resistance.
iii. Sternocostal head is made prominent by abducting
arm to 60' and then touching the opposite hip
(Fig. 3.23).
iv. Press the fists against each other (Fig.3.2q.

Clovipeclorol Foscio
Clavipectoral fascia is a fibrous sheet situated deep to
the clavicular portion of the pectoralis major muscle. It
extends from the clavicle above to the axillary fascia
below. Its upper part splits to enclose the subclaoius
muscle (Fig. 3.12). The posterior lamina is fused to the
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